Breakerless ignition system



April 23, 1963 B. H. SHORT ETAL BREAKERLESS IGNITION SYSTEM Filed March 13, 1961 INVENTORS Brooks H.Shorf BY Richard L.Konopa Their Attorney This invention relates to ignition systems for internal combustion engines wherein no breaker contacts are required and wherein a semiconductor such as a transistor controls current flow to the primary winding of an ignition coil.

The ignition system as used with the engines of present day motor vehicles includes a pair of breaker contacts that are operated by a cam driven by the engine. The breaker contacts control the current flow to the primary winding of an ignition coil and are subjected to severe punishment due to the constant opening and closing of the contacts and the arcing of the contacts when they open. As a result of this punishment, the breaker contacts must be periodically replaced to provide optimum engine operation.

It is an object of this invention to provide an ignition system where no breaker contacts are required and where the current flow to the ignition coil is controlled by a semiconductor switching means such as a transistor.

Another object of this invention is to provide an ignition system for an internal combustion engine wherein a semiconductor controls current flow to the primary of an ignition coil and wherein the timing of conduction and noneonduction of the semiconductor is controlled by pulse generating means that is capable of delivering pulses of voltage whose timing is determined by the speed or load conditions of the engine or both.

A further object of this invention is to provide an ignition system wherein current flow to the primary winding of an ignition coil is controlled by a semiconductor and wherein the conduction and noneonduction of the semiconductor is controlled by the charging and discharging of a capacitor which is charged and discharged under the control of timing means driven by the engine.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic illustration of a breaker-less ignition system made in accordance with this invention.

FIGURE 2 is a View illustrating a portion of the pulse generating means shown in FIGURE 1.

FIGURE 3 is another view illustrating a portion of the pulse generating means of FIGURE 1.

Referring now to the drawings and more particularly to FIGURE 1, the reference numeral has been used to designate an internal combustion engine which has a carburetor 12 and a spark plug 14 for igniting the combustible mixture of the engine. Only one spark plug is illustrated but it will be apparent that there will be as many spark plugs as there are cylinders. In this ignition system to be described, it is assumed that the engine 10 is an eight cylinder engine.

The ignition system of FIGURE 1 includes a pulse ice generating means which is generally designated by reference numeral 16. This pulse generating means includes a shaft 18 which is driven by the engine 10. The shaft 18 is suitably journalled in a housing or base not shown and is connected with a plate member 20 which is illustrated in FIGURE 2. A second plate member 22 is rotatably supported by the shaft 18 and carries a magnetic assembly including parts 24, 26, and 28. The parts 24 and 28 are of identical configuration and have a plurality of radially extending fingers as is better illustrated in FIGURE 3. The part 26 is a permanent magnet preferably of the ferrite type. The radially extending fingers of parts 24 and 28 are aligned and pass a U-shaped core member designated by reference numeral 30 upon which is wound a pick-up coil 32.

The U-shaped core member 30 with its coil winding 32 is mounted on a rotatable timing plate 34 which is journalled for rotation on any suitable base or housing not shown. The plate 34 rotates around the axis of the shaft 18 and is rotated by a vacuum unit 36. This vacuum unit contains the usual diaphragm 38 and a spring 40 for urging the diaphragm in one direction. The vacuum unit is connected with the intake manifold side of the engine 10 via a pipe 42. It thus is seen that the timing plate 34 will be rotated in accordance with the vacuum existing in the intake manifold of the engine and that the rotation of this plate therefore will be an indication of load conditions in the engine.

The plate member 22 which may rotate with respect to shaft 18 supports a pair of fly weights 44 and 46 which are best illustrated in FIGURE 2. These fly weights are pivoted to the plate 22 on the pins 48 and 50 and springs are interposed between the pins 48 and 50 and pins 52 and 54 which are attached to the cam plate 20. As the shaft rotates, the fly weights 44 and 46 are thrown outwardly and since they engage the cam plate 20, they will cause the plate 22 to rotate relative to the shaft 18. This will, of course, adjust the magnetic assembly 24, 26, and 28 relative to the shaft 18 and this arrangement therefore provides a centrifugal advance mechanism for adjusting the magnetic assembly relative to the shaft 18. This, as will become more readily apparent hereinafter, will effect the timing of the engine in accordance with engine speed.

When the shaftlS is rotating, it will be apparent that a pulse of voltage will be induced in the pickup coil 32 when the fingers of the magnetic assemblies 24 and 28 pass by the tips of the U-shaped core member 30. There will be eight voltage pulses for every revolution of the shaft 18 and the timing of these voltage pulses can be varied both by the centrifugal advance mechanism and by the vacuum control unit 36. It therefore is seen that the voltage pulses that are induced in the coil winding 32 will be timed both as to speed of the engine 10 and as to the load conditions of the engine 10.

The pick-up coil 32 has one side thereof connected with the junction 56 and has an opposite side connected with the lead wire 59. The junction 56 can be connected to one side of a battery 58 through the ignition switch 60. The opposite side of the battery 58 is connected directly to ground as is shown.

The junction 56 is connected with the junction 62 by the lead wire 64. The junction 62 is connected with the emitter electrode of a PNP transistor generally designated by reference numeral 66. This transistor has a base electrode connected with junction 68 and has a collector electrode connected with the junction '70. The junction 70 is connected to one side of a resistor 72, the opposite side of this resistor being connected to ground.

The ignition system includes another PNP transistor 74 which has an emitter electrode connected with the junction 76. A resistor 78 is connected between junctions 76 and 80. The base electrode of transistor 74 is connected with the junction 82 and it is seen that a capacitor 84 is connected between the junctions 70 and 82. The collector electrode of transistor 74 is connected with junction 86 and it is seen that a resistor 88 connects the junctions 68 and 86. Another resistor 90 is connected between junction 82 and ground. A resistor 81 is connected to junction 86. The other side of this resistor is connected to ground.

The junction 80 is connected with the emitter electrode of a third PNP transistor 92. The base electrode of transistor 92 is connected with junction 76 whereas the collector electrode of transistor 92 is connected with a resistor 94. The opposite side of resistor 94 is connected with the primary winding 96 of an ignition transformer 98. The secondary winding 100 of this ignition transformer is connected with the rotor contact 102 that cooperates with the electrodes 104 on a conventional distributor cap. The contacts 104 are connected respectively with the spark plugs 14 via the lead wires 106. It is understood that the opposite side of the spark plugs are connected to ground in the usual manner. It is seen that the primary and secondary windings 96 and 100 of the ignition coil are tied together at junction 108 and this junction is connected to ground.

When it is desired to start the engine or maintain it in a running condition, the ignition switch 60 is closed. This causes the lead wire 64 and junctions 56, 62 and 80 to all be connected with the positive side of the battery 58. If it is assumed that the radial pole tips of the magnetic parts 24 and 28 are not in alignment with the U-shaped core 30, there is no pulse of voltage developed in the pick-up coil 32. As a result of this, the transistor 66 will be substantially fully non-conductive between emitter and collector since its emitter to base voltage is substantially equal due to the fact that the emitter and base electrodes are connected by the pick-up coil 32. When there is no emitter to collector current flow in the transistor 66, there will be no voltage developed across the resistor 72. The junction point 70 will therefore be at substantially ground potential since it has no connection to junction 62 through the emitter-collector path of transistor 66.

The transistor 74 at this time will be conductive between emitter and collector since its base is connected substantially with ground potential via resistor 90 while its emitter is connected with the positive side of the battery via resistor 78. The capacitor 84 will now be charged via a circuit that may be traced from the junction 80', through the parallel paths of resistor 78 and the emitter to base circuit of transistor 92, thence through the emitter to base junction of transistor 74, through capacitor 84 and thence through resistor 72 to ground. The capacitor 84 will charge up to very near battery potential.

With transistor 74 conducting between emitter and collector due to its base circuit being completed to ground via resistor 90, there now is a base current path for transistor 92 via the emitter to collector circuit of transistor 74 and through resistor 91 to ground. With a base current path for transistor 92, it becomes substantially fully conductive between its emitter and collector to therefore supply a maximum amount of current to the primary winding 96 of the ignition coil 98. This current is, of course, limited by the resistor 94.

From the foregoing description, it can be seen that during the time that a pulse of voltage is not generated in pick-up coil 32, the transistors 74 and 92 are turned fully on whereas the transistor 66 is maintained fully off. During this time, the capacitor 84 is charged to substantially battery potential.

As the shaft rotates, the radial pole tips of magnetic parts 24 and 28 will of course pass the U-shaped core member 30 during a part of the revolution of shaft 18 and cause a pulse of voltage to be induced in the coil winding 32. When a pulse of voltage is induced in the coil winding 32, it is of such a polarity as to cause the base of transistor 66 to become negative with respect to the emitter and therefore cause emitter to base current to flow in transistor 66. With emitter to base current flowing in transistor 66, it turns fully on between emitter and collector. It can be seen that when the emitter to collector circuit of transistor 66 is substantially fully conductive, the capacitor 84 is now essentially connected between the base and emitter electrodes of transistor 74. Since capacitor 84 was previously charged to battery potential, this voltage will now appear across the emitter to base circuit of transistor 74 and will be of such a polarity as to cause the base of transistor 74 to become positive with respect to the emitter. This will cut off the conduction of transistor 74 between emitter and collector. With transistor 74 nonconducting between emitter and collector, the base and emitter electrodes of transistor 92 are now connected to substantially the same potential via resistor 78 and therefore the transistor 92 will be nonconductive between emitter and collector.

When transistor 92 turns off between emitter and collector, the current flow path to the primary winding 96 is suddenly cut off and the collapsing magnetic field in the ignition coil 98 will, of course, cause a high voltage pulse to appear at the secondary winding 100 of the ignition coil and therefore cau-se a spark to jump at the electrodes of the spark plug 14. It thus is seen that the generating of a voltage pulse in the pick-up coil winding 32 has set into motion a series of events through the transistorized circuit which caused the transistor 92 to suddenly become nonconductive and therefore cause a firing of one of the spark plugs in engine 10.

It is pointed out that the time that transistors 74 and 92 are turned oif is dependent upon the RC time constant of resistor and capacitor 84. This is true since the capacitor 84 discharges through a path that includes resistor 90, the battery 58, and the emitter to collector circuit of transistor 66.

The resistor 88 is a feed-back resistor which acts to keep transistor 66 turned on as long as transistor 74 is turned ofi. and which will turn transistor 66 off as soon as transistor 74 returns to the on condition. Thus as transistor 74 is being turned oif, the junction point 86 becomes more nearly that of ground potential so that transistor 66 remains turned on when voltage is being developed across the pick-up coil 32. On the other hand, as transistor 74 again becomes conductive, the junction 86 becomes more nearly that of the positive side of the battery to insure a nonconductive condition of transistor 66. This feed-back resistor is therefore an aid to the primary control by the voltage generated in the pick-up coil in switching transistor 66 on and ofi. The primary control, of course, is always determined by the voltage generated in the pick-up coil 32.

It will be apparent from the foregoing description that the transistor 92 controls current flow to the primary winding 96 of the ignition coil 98 to therefore control the timing of the ignition pulses supplied to the spark plugs 14 of the engine. Conduction of transistor 92 is controlled by the transistorized circuitry connected therewith and this circuitry is in turn controlled by the voltage pulses generated in pick-up coil 32. The voltage pulses generated in pick-up coil 32 are timed both in accordance with the speed of the engine and load conditions of the engine due to the provision of the vacuum advance control unit 36 and the centrifugal advance mechanism as illustrated in FIGURE 2. The switching on and off of transistor 92 will thus be controlled both as to load and speed conditions of the engine 10.

While the embodiments of the present invention as herein disclosed, constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In combination, an internal combustion engine having a spark plug for firing the combustible mixture of said engine, an ignition coil having a primary Winding and a secondary winding, means connecting said secondary winding with said spark plug, a source of voltage, semiconductor switch means connected between said source of voltage and the primary winding of said ignition coil for controlling the current flow through said primary winding, a pulse voltage generating means including spaced relatively rotatable parts located in a magnetic circuit with each other, said pulse voltage generating means being mechanically coupled with said engine and including centrifugal advance means and vacuum advance means, means connecting said vacuum advance means with the intake manifold of said engine, and mean-s electrically connecting said pulse generating means with said semiconductor switch means.

2. In combination, an internal combustion engine having a spark plug, an ignition coil having a primary winding and a secondary winding, means connecting said secondary winding with said spark plug, a transistor having emitter, base and collector electrodes, a source of voltage, means connecting the emitter-collector circuit of said transistor between said source of voltage and the primary winding of said ignition coil, a device for generating pulses of voltage mechanically coupled to said engine, said device including centrifugal advance and vacuum advance means and having spaced relatively rotatable parts located in a magnetic circuit with each other, means connecting said vacuum advance means with the intake manifold of said engine, and means for varying a voltage applied to the base electrode of said transistor in accordance with the voltage output of said device.

3. An ignition system for an internal combustion engine comprising, a spark discharge device adapted to ignite the combustible mixture of said engine, an energizing circuit for said spark discharge device, a first transistor connected with said energizing circuit having emitter, base and collector electrodes, a second transistor having emitter, base and collector electrodes, a source of voltage connected with said first transistor, a capacitor, a charging circuit for said capacitor including the emitterbase circuit of said first transistor, a discharging circuit for said capacitor including the emitter-collector circuit of said second transistor, pulse generating means driven by said engine, and means connecting said pulse generating means directly across the emitter-base circuit of said second transistor.

4. An electrical ignition system for igniting the combustible mixture of an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, a source of voltage, a first transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said first transistor between said voltage source and said primary winding, a second transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said second transistor across said voltage source, means connecting the emitter electrode of said second transistor with the base electrode of said first transistor, a third transistor having emitter, base and collector electrodes, a capacitor connected between the collector electrode of said third transistor and the base electrode of said second transistor, means connecting the emittercollector circuit of said third transistor across said voltage source, and means operating in synchronism with said engine for varying the voltage applied to the base electrode of said third transistor.

5. An ignition system for igniting the combustible mixture of an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, a source of voltage, a first transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said first transistor between said voltage source and said primary winding, a second transistor having emitter, base, and collector electrodes, means connecting the emitter-collector circuit of said second transistor across said voltage source, means connecting the base electrode of said first transistor with the emitter electrode of said second transistor, a third transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said third transistor across said voltage source, a capacitor connecting the collector electrode of said third transistor with the base electrode of said second transistor, means for varying the base voltage of said third transistor in synchronism with operation of said engine, and a feedback circuit connecting the collector electrode of said second transistor with the base electrode of said first transistor.

6. In combination, an internal combustion engine having a spark plug for firing the combustible mixture of said engine, an ignition coil having a primary winding and a secondary winding, means connecting said secondary Winding with said spark plug, a voltage source, a first transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said first transistor between said voltage source and the primary winding of said ignition coil, a second transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said second transistor across said voltage source, means connecting the emitter electrode of said second transistor with the base electrode of said first transistor, a third transistor having emitter, base and collector electrodes, means connecting the emitter-collector circuit of said third transistor across said voltage source, a capacitor connecting the collector electrode of said third transistor with the base electrode of said second transistor, pulse generating means driven in synchronism with said engine, and means connecting said pulse generating means across the emitter and base electrodes of said third transistor.

7. The combination according to claim 6 wherein the pulse generating means has vacuum control means connected with the intake manifold of the engine for adjusting the output voltage of the pulse generating means in accordance with vacuum conditions of the engine.

8. The combination according to claim 6 wherein the pulse generating means includes centrifugal means for adjusting the output voltage of the pulse generating means in accordance with engine speed.

9. In combination, an internal combustion engine having a spark plug for firing the combustible mixture of said engine, an ignition coil having a primary winding and a secondary winding, means connecting said secondary winding With said spark plug, a source of voltage, semiconductor switch means connected between said source of voltage and the primary wind-ing of said ignition coil for controlling the current flow through said primary Winding, a biasing circuit for said semiconductor switch means connected with said voltage source in such a manner that said semiconductor switch means is normally conductive, a pulse voltage generating means, said pulse voltage generating means being mechanically coupled with said engine and including centrifugal advance means, and means electrically connecting said pulse generating means with said semiconductor switch means whereby said semiconductor switch means is periodically turned oif by voltage pulses coming from said pulse generating means.

10. In combination, an internal combustion engine hav- 7 ing a spark plug for firing the combustible mixture of said engine, an ignition coil having a primary winding and a secondary Winding, means connecting said secondary winding with said spark plug, a source of voltage, semiconductor switch means connected between said source of voltage and the primary winding of said ignition coil for controlling the current flow through said primary winding, a biasing circuit for said semiconductor switch means connected with said battery and normally biasing said semiconductor switch means to a conductive state, a pulse generating means, said pulse generating means being mechanically coupled with said engine and includ- 8 ing centrifugal advance means and vacuum advance means, means connecting said vacuum advance means with the intake manifold of said engine, and means electrically connecting said pulse generating 'means' with said semiconductor switch means.

References Cited in the file of this patent UNITED STATES PATENTS 2,474,550 Short et a1 June 28, 1949 2,918,911 Guiot Dec. 29, 1959 2,918,913 Guiot Dec. 29, 1959 2,953,719 Guiot Sept. 20, 1960 

1. IN COMBINATION, AN INTERNAL COMBUSTION ENGINE HAVING A SPARK PLUG FOR FIRING THE COMBUSTIBLE MIXTURE OF SAID ENGINE, AN IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANS CONNECTING SAID SECONDARY WINDING WITH SAID SPARK PLUG, A SOURCE OF VOLTAGE, SEMICONDUCTOR SWITCH MEANS CONNECTED BETWEEN SAID SOURCE OF VOLTAGE AND THE PRIMARY WINDING OF SAID IGNITION COIL FOR CONTROLLING THE CURRENT FLOW THROUGH SAID PRIMARY WINDING, A PULSE VOLTAGE GENERATING MEANS IN- 